1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device, and more particularly, to a method of fabricating a trench isolation structure by using a high-density plasma chemical vapor deposition apparatus.
2. Description of the Related Art
As a type of technology for providing device isolation in highly-integrated semiconductor devices, a shallow trench isolation (hereinafter, referred to as ‘STI’) fabricating method has been widely applied. In the STI process, in order to prevent the occurrence of defects and to make device characteristics stable, an oxide film liner and a nitride film liner are sequentially formed on the side walls and bottom surface of an STI trench, and then the trench is filled with a high-density plasma (hereinafter, simply referred to as ‘HDP’) oxide film, thereby forming the STI structure.
However, with continued pressure for higher integration, as the design rule of a semiconductor device decreases, the aspect ratio of the STI structure increases, and the width of the gap of the STI trench decreases. Accordingly, the ability to fill the gap inside the STI trench without producing voids has increased in importance.
In order to ensure an excellent gap filling property, a method of increasing a bias power in the HDP process can be used. However, when the bias power is increased, the oxide film 12 and the liner 13 of the side walls and bottom of the STI trench are more likely to become separated from the surface of the substrate 10, as shown in the TEM (Transmission Electron Microscopy) photograph of FIG. 1. Further, as shown in the SEM (Scanning Electron Microscopy) photograph of FIG. 2, multiple bubble defects 16 may occur in the HDP oxide film 14.
In order to prevent the above-described separation phenomenon and bubble defects, there has been suggested a method in which a medium-temperature oxide liner is additionally formed on the nitride liner. However, in this case, the gap is further decreased due to the additional medium-temperature oxide liner having a thickness of about 50 to 300 Å, which causes a drastic decrease in the gap filling margin. Further, an additional chemical vapor deposition (hereinafter, simply referred to as ‘CVD’) process is required, which can complicate and lengthen device fabrication time.